A letter report issued by the Government Accountability Office with an abstract that begins "The Department of Labor's Mine Safety and Health Administration (MSHA) appropriately did not use recent trend data on coal workers' pneumoconiosis (CWP) as a basis for its proposal to lower the permissible exposure limit for respirable coal mine dust. These recent data from the Department of Health and Human Services' National Institute for Occupational Safety and Health (NIOSH) are inappropriate for this purpose because they do not include the types of detailed information about individual miners needed to estimate the likelihood that miners would develop CWP at different exposure levels, such as historical dust exposures. MSHA primarily based its proposed new limit on two reports and six epidemiologic studies, which each concluded that lowering the limit on exposure to coal mine dust would reduce miners' risk of developing disease. MSHA's proposed coal mine dust limit was supported by these reports and studies because, unlike recent CWP trend data, they included information needed to conduct a reliable epidemiological analysis of disease risks associated with different levels of exposure to coal mine dust."